1. Field of the Invention
The present invention relates to a semiconductor memory card that stores audio data, still image data and control data, and to a playback apparatus, recording apparatus, playback method, recording method, and computer-readable recording medium relating to such a semiconductor memory card. In particular, the present invention relates to improved storage of audio data, image data and control data distributed as contents by a content distribution service, such as an electronic music distribution service.
2. Description of Background Art
Electronic music distribution enables users to purchase and receive music contents (e.g., songs and albums) via the Internet. Such technology has the potential to greatly change the market for recorded music and is gradually becoming possible as the necessary infrastructure is introduced. One way to store music contents that are obtained from an electronic music distribution service is on semiconductor memory cards whose portability makes them ideal. Accordingly, a great increase is expected in the demand for such cards.
Music contents are not restricted to merely containing audio data. As one example, “mixed-media” audio contents can include related images that are to be displayed when music is played back. Such mixed-media audio contents can be used for “karaoke software” that is composed of a backing audio track and images for the lyrics of a song and a background. It is believed such mixed-media audio contents will also be subject to electronic music distribution, so that it is necessary to consider how such contents should be stored in a semiconductor memory card.
The following describes how mixed-media music contents are stored on a recording medium, such as a CD (Compact Disc), which is to say, how audio data and image data are conventionally stored on a recording medium.
To enable a player to play back music and display images, a conventional mixed-media music content is recorded onto a recording medium as multiplexed data produced by multiplexing audio data for the music with image data for the lyrics and/or background images. When the multiplexed data is reproduced, the image data can be displayed while the audio data is being played back.
A CD-Graphics disc is one example of a medium that enables image data to be displayed while audio data is being played backed by having such data multiplexed together. When producing a CD-Graphics disc, data is multiplexed in units composed of 16-bit main codes and subcodes. Audio data is assigned to the 16-bit main codes, while image data for lyrics, background images and the like is assigned to the subcodes. When playback commences for any of the music contents recorded on a CD-Graphics disc, the audio data assigned to the 16-bit main codes is successively played back while the image data assigned to the subcodes is successively displayed.
When audio data and image data are multiplexed together in this way, it becomes necessary to provide separate images to each music content in a music album. This means that in this conventional multiplexing method, a disc producer has had to go to the trouble of producing at least one image for each music content.
It is believed that fans of major recording artists will appreciate having a different image for each song (music content) on an album. Since such artists can expect to sell many copies of their albums, the cost of providing such extra material should be covered by sales.
However, minor artists cannot expect high sales for their work even if different images are provided for each song, so that the cost of providing such material may not be offset by sales.
In this way, the commercial effect that results from the money and effort expended in the production of images will greatly differ depending on whether the artist is popular. With conventional discs, however, it is necessary to assign at least one image to each music content regardless of how popular the recording artist is or of how many sales can be expected. As a result, producers are dissatisfied with conventional media.